Current wireless communication devices may be configured to support cellular network communications using a variety of technologies and formats depending on the service provider of choice. Examples of cellular networks include Third Generation (3G), Fourth Generation (4G), Long Term Evolution (LTE), Time Division Multiple Access (TDMA), Frequency Division Multiple Access (FDMA), Code Division Multiple Access (CDMA), Wideband CDMA (WCDMA), Time Division Synchronous CDMA (TD-SCDMA), Global System for Mobile Communications (GSM), and Universal Mobile Telecommunications Systems (UMTS). In order to store the necessary provisioning data that allows the mobile device to communicate with a wireless communications network, wireless communication devices may utilize a subscriber identity module (SIM) provided on a smart card such as a universal integrated circuit card (UICC).
Multi-SIM mobile communication devices have become increasingly popular because of their flexibility in service options and other features. For example, a dual-SIM dual-standby (DSDS) device is a type of multi-SIM mobile communication device configured with one radio frequency (RF) resource and two SIMs, and typically allows selective communication on a first network through a radio access technology (RAT) while listening for pages on a second network through another RAT. Multi-SIM communication devices may allow a user to implement two different wireless communication service subscriptions or plans with different service providers, with separate numbers and bills, on the same device (e.g., business account and personal account).
In a DSDS device, the two subscriptions share one RF resource. That means that when one subscription is active, the other subscription is idle and not using the RF resource. However, the idle subscription may periodically interrupt the active subscription to perform idle mode wakeup using the shared RF resource. This process of switching access of the shared RF resource from an active subscription to an idle subscription is sometimes referred to as a “tune-away” because the RF resource tunes away from the active subscription's frequency band or channel and tunes to the idle subscription's frequency bands or channels. After the idle subscription has finished network communications during the idle mode wakeup, access to the RF resource may tune from the idle subscription back to the active subscription (sometimes referred to herein as a “tune-back”).
During travel, users may obtain and install local SIM cards in their mobile communication devices in order to pay local call rates in the destination country. By using multiple SIMs, a user may take advantage of different service pricing plans and save on mobile data usage. However, users may be limited by the number of UICCs supported by the multi-SIM mobile communication device (e.g., a dual-SIM device supports two UICCs). Further, users may be inconvenienced by having to use different telephone numbers (e.g., MSISDNs) for different local services, as well as by the barriers to accessing personal data (e.g., a contacts list that is normally stored on a SIM) across multiple SIMs. Moreover, while a user may obtain service while roaming from his or her home network operator without purchasing or installing additional SIMs, the user is often charged a very high fee for such service.
To overcome the costs and challenges of utilizing physical SIMs in a roaming environment, a virtual SIM (VSIM) may be implemented. A VSIM does not have to be implemented in hardware such as a UICC, but instead may be implemented in software, for example as a VSIM module stored in memory on the mobile communication device. The VSIM module works in conjunction with a remote server that contains an actual physical SIM card. The SIM card on the server, which may be termed a remote VSIM server or network SIM server, stores a SIM profile that may be sent to the VSIM module on the mobile communication device using the subscription supported by the device's physical SIM. Once the SIM profile is loaded in the VSIM module, the VSIM module may behave like a regular SIM card and support a subscription with a local network operator (“VSIM network”).
Upon connecting to the VSIM network, the VSIM network sends an authentication request to the mobile communication device. The mobile communication device then performs a tune-away from the VSIM subscription and to the subscription on the physical SIM to communicate with the remote VSIM server, which provides authentication services. The mobile communication device remains tuned to the physical SIM subscription until it provides an authentication response. The mobile communication device then tunes back to the VSIM subscription and sends the authentication response to the VSIM network in order to utilize network services. However, due to timing issues associated with authenticating a VSIM with a remote VSIM server and the limitations imposed on use of a shared RF resource, it may be difficult for a multi-standby mobile communication device, such as a DSDS device, to complete the VSIM authentication request without dropping one or more network connections.